Add ability for users to sort cards in "My Cards" page

Users can now sort cards by the following fields

 - Date created at
 - Due date
 - Board

When sorting cards by board they are not grouped by board name, just by the board they belong to. This is because Mongoose doesn't support sorting by fields from referenced documents. Changing this would need a big refactor and would have a negative impact on performance. Not sure if it is worth it?

Sorting also works with other filters.